The amino acid sequences of the subunits of bovine heart cytochrome c oxidase are the objects of the present investigation. The 11.6K dalton heme subunit has been completely sequenced and the 22K dalton Cu-subunit is about 60 percent completed. The latter will be completely sequenced during the coming year. The sequence determination of Pseudomonas putida cytochrome P-450 will be the major effort of the year. Tryptic peptides are now being purified and will be sequenced. Cyanogen bromide fragments have been isolated and they will be purified during the coming year. NH2-terminal sequences of some of the rabbit liver microsomal cytochrome P-450 other than the (LM2)-form will be sequenced if pure forms are isolated during the coming year in order to compare the sequences of the bacterial and animal cytochrome P-450s.